Direct Experimental Evidence for Markedly Enhanced Surface Proton Activity Inherent to Water Ice
Direct Experimental Evidence for Markedly Enhanced Surface Proton Activity Inherent to Water Ice
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水冰固有的表面质子活性显着增强的直接实验证据
DOI：
10.1021/acs.jpclett.0c00384
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Matsumoto Yoshiyasu
中科院分区：
文献类型：
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作者：
Kato Fumiaki;Sugimoto Toshiki;Matsumoto Yoshiyasu
自电离和随后的质子转移过程决定了水分子系统固有的质子活性。在这项研究中，我们通过同时观察由H2O和D2O组成的明确双层冰膜表面和内部水分子的H/D交换，提供了直接的实验证据，表明结晶冰表面的质子活性显着增强。热解吸质谱显示出源自表面 H/D 交换平衡的清晰特征，而红外吸收光谱表明内部没有明显的 H/D 交换进展。详细的动力学分析表明，表面的 H/D 交换速率比内部至少高 3 个数量级。质子活性的急剧增强表明与本体中的质子相比，表面水合质子的浓度极高。我们的结果还强调了局部氢键结构对水分子自电离的影响。
Autoionization and subsequent proton transfer processes determine the proton activity inherent to water molecular systems. In this study, we provide direct experimental evidence that the proton activity is markedly enhanced at the surface of crystalline ice, on the basis of the simultaneous observation of H/D exchange of water molecules at the surface and in the interior of well-defined double-layer ice films composed of H2O and D2O. Thermal desorption mass spectrometry showed clear signatures derived from the surface H/D exchange equilibrium, whereas infrared absorption spectroscopy indicated no appreciable H/D exchange progress in the interior. Detailed kinetic analyses revealed that the rate of H/D exchange at the surface is at least 3 orders of magnitude higher than in the interior. This drastic enhancement of the proton activity suggests an extremely high concentration of surface-hydrated protons in comparison with those in the bulk. Our results also highlight the impact of the local hydrogen-bond structure on the autoionization of water molecules.